array to string error when create notification

so i wanna create notification in laravel but this error occur

"Array to string conversion (SQL: insert into admin_notifications (id, type, data, notifiable_id, notifiable_type, updated_at, created_at) values ▶"

this is my model

   <?php

namespace App;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Notifications\DatabaseNotification;
class admin_notification extends Model
{
    protected $table = 'admin_notifications';
    protected $fillable = ['id','type','data'];

}

thank you

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